This invention relates to a driving mechanism for a three-position electrical switch comprising a jump-drive sub-assembly having a switching shaft which is rotatable between ON, OFF and EARTH switching positions, and a storage drive sub-assembly having a disconnecting spring which releases its stored spring force when a fuse is blown or an open circuit trip has occurred.
Existing driving mechanisms for three-position electrical switches require large operating forces. Additionally, high breaking forces are required when a circuit is interrupted by a blown fuse. Furthermore, existing storage drive sub-assemblies take up a large amount of space. Also, a switching operation from ON to OFF can be carried out only by the storage drive sub-assembly, and not by the jump drive sub-assembly (see for example instructions for use for closed circuit installations of the NSM type from October 1969, Brush Switch Gear Limited England).